Paragraf announces working partnership with CERN

2 min read

Paragraf, the Cambridge spin-out specialising in graphene, has announced that it has established a working partnership with the Magnetic Measurement section at CERN, the European Organisation for Nuclear Research.

Both parties are set to release a joint whitepaper demonstrating how new opportunities for magnetic measurements are being opened up through the use of Paragraf's graphene sensors, in particular because ot it's negligible planar Hall effect.

The Magnetic Measurements section at CERN is in charge of testing magnets for the accelerator operated at the facility, and uses the latest-available techniques and instruments. High precision and reliable measurements are performed for many of CERN's ongoing projects that require new sensors and transducers to help improve their measurement methods and accuracy.

Commenting Simon Thomas, CEO at Paragraf said, “This collaboration with CERN demonstrates the potential of graphene-based Hall effect sensors to improve accuracy in magnetic measurement applications. Our Hall effect sensors address key challenges CERN is facing in mapping magnetic fields, namely: highly accurate measurements of local field distributions in accelerator magnets, while eliminating artefacts and reducing uncertainties stemming from the sensors.”

Existing Hall effect sensors all exhibit planar Hall effects where field components which are not perpendicular to the sensing plane produce false signals. This is because the sensing layer is effectively three-dimensional, with some amount of depth. These false signals, together with the non-linear response to the field strength, increase the measurement uncertainty and thus limit the application of Hall sensors. Separating the true signals from the systematic errors is a complex and time-consuming process.

The Hall effect sensor from Paragraf solves these problems because the active sensing component is made of atomically thin graphene, which is therefore two-dimensional, and truly only senses magnetic fields along one direction; giving a negligible planar Hall effect. This enables the true perpendicular magnetic field value to be obtained, allowing for higher precision mapping of the local magnetic field.

“Using Hall effect sensors without planar effect would open the door to a new mapping technique by mounting a stack of sensors on a rotating shaft. The compelling advantage would be measurements of the harmonic content in accelerator magnets almost point-like along the magnet axis”, said Stephan Russenschuck, head of the magnetic measurement section at CERN.

One of the other key properties of Paragraf’s Hall effect sensor is its wide temperature range from +80°C down to cryogenic temperatures of 1.5 Kelvin. For CERN, this means that fields inside the superconducting magnets could be measured with high accuracy, using sensors operating in liquid helium temperature ranges (below -269 °C, 4 Kelvin, -452 °F) where the calibration of sensors is less than trivial.

CERN’s Magnetic Measurement section is looking to perform more in-depth tests on the Hall effect sensors, with the eventual aim of using them to build a novel mapping system for magnetic fields.

Paragraf and CERN will also be releasing a joint white paper communicating the work to date in more detail and showcasing the lack of planar Hall effect in Paragraf’s sensors, as well as detailing its high performance across a range of magnetic fields.